Fasteners such as nails and staples are commonly used in projects ranging from crafts to building construction. While manually driving such fasteners into a work piece is effective, a user may quickly become fatigued when involved in projects requiring a large number of fasteners and/or large fasteners to be driven into a work piece. Moreover, proper driving of larger fasteners into a work piece frequently requires more than a single impact from a manual tool.
In response to the shortcomings of manual driving tools, power-assisted devices for driving fasteners into work pieces have been developed. Contractors and homeowners commonly use such devices for driving fasteners ranging from brad nails used in small projects to common nails which are used in framing and other construction projects. Compressed air has been traditionally used to provide power for the power-assisted (pneumatic) devices. However, other power sources have also been used, such as DC motors.
Various safety features have been incorporated into pneumatic and other power nailers. One such device is commonly referred to as a work contact element (WCE). A WCE is incorporated into nail gun designs to prevent unintentional firing of the nail gun. A WCE is typically a spring loaded mechanism which extends outwardly from the portion of the nail gun from which a nail is driven. In operation, the WCE is pressed against a work piece into which a nail is to be driven. As the WCE is pressed against the work piece, the WCE compresses the spring and generates an axial movement which is transmitted to a trigger assembly. The axial movement is used to reconfigure a safety device, which is typically a trigger disabling mechanism, so as to enable initiation of a firing sequence with the trigger of the nail gun.
Since typical WCE arrangements in the past have included a mechanical linkage between the WCE and the trigger, it would be advantageous to provide an additional safety feature that is not necessarily linked with trigger operation. It would also be advantageous if such safety feature interacted with the firing mechanism to block operation of the firing mechanism if the WCE is not depressed.